i know im not a guru or anything and i dont know much about fans to recommend any but i thought it might help the next people who read this to know what you are trying to cool....you said you are building a new computer so im guessing you are wanting some case fans and a cpu fan? might also help if you posted your build so we know what your trying to cool so the tech wizards can tell you the appropriate fan/s. also how much are you wanting to spend.

I would recommend the Scythe SFF21F and the SFF21E as quiet fans that push a decent amount of air. The Nexus D12SL-12 (also available as the Yate Loon D12SL-12) is another great fan, as is the Noctua NF-S12. All of them have a more-or-less silent noise profile at full speed and they push a reasonably good amount of air at this speed.